(a) Field of the Invention
The present invention relates to a novel catalyst composition which contains a zeolite composition improved in catalytic properties or the zeolite composition and metal component having hydrogenation activity.
(b) Description of the Related Art
Catalysts containing zeolites have been used extensively in catalytic reactions, for example, various conversion reactions of hydrocarbons, such as hydrogenolysis, including hydrocracking, catalytic cracking, isomerization, alkylation, dealkylation, disproportionation, olygomerization, aromatization, hydrogenation, dehydrogenation and reforming, and, further, conversions of oxygen-containing hydrocarbons, such as methanol, and hydrogenation of carbon monoxide. The zeolites to be used in these reactions as catalysts or catalyst components have generally been modified to control or improve the catalytic properties, such as acidity or hydrothermal resistance. There have been proposed various methods for modifying zeolites. The most conventional modification is dealumination, which provides various modified zeolites which are controlled or improved in acidity or hydrothermal resistance. Dealumination has been performed by various methods, for example, gaseous phase dealuminations, such as steaming and treatment with gases containing hydrochloric acid, and wet dealuminations, such as treatment with aqueous mineral acid solutions and treatment with various aqueous metal salt solutions. Zeolites have been modified by not only these dealuminations but also other methods, for example, substitution of a part of Si or Al in zeolite lattice with other atoms, such as Ti, Ga or Fe.
Dealumination generally has the effects of increasing acid strength per acid point of zeolites and improving the hydrothermal resistance of zeolites themselves, but has a shortcoming of decreasing active points (particularly acidity).
Also, zeolites have generally been mixed with binders, such as alumina, to improve mechanical strength of catalysts. Further, loading of compositions comprising zeolites and alumina (or zeolites alone) with hydrogenation metals, such as metals of Groups VIA and VIII of the Periodic Table, is a conventional means for imparting the catalysts with not only acidity but also sufficient hydrogenation properties.
These are no more than typical examples of various conventional methods of modifying zeolites and preparing catalysts to improve catalytic properties of zeolites-containing catalysts, and there are many other reports concerning hydrocarbon conversion catalysts alone.
As to known catalysts containing non-dealumination type zeolites, U.S. Pat. No. 3,269,934 and U.S. Pat. No. 4,021,331 describe hydrocracking catalysts containing hydrogen-type (H.sup.+ -type) of zeolite Y or ZSM-20. These zeolites however have a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of 8 or less, and the too much Al content causes various problems, such as insufficiency in acidity and hydrothermal resistance, requiring further modification, such as the dealumination described above.
As to known catalysts containing zeolites modified by dealumination, Japanese Patent Application Kokai Koho (Laid-open) Nos. 58-147495 and 58-207949 and Japanese Patent Application Kokoku Koho (Publication) No. 4-12317 describe methods of catalytic cracking of hydrocarbons by using catalysts which are prepared by using dealuminated zeolites having expanded pores. Although these zeolites are improved in thermal resistance and acidity by the dealumination as described above, the catalytic activities are decreased due to a decrease in the acid density of the zeolites themselves.
Japanese Patent Application Kokai Koho (Laid-open) No. 60-225646 describes hydrocracking by using catalysts which are prepared by mixing a dealuminated zeolite with a binder, such as alumina, and loading the resulting composition with transition metals having hydrogenation function. Even the binder, however, has almost no effect of improving catalytic activities, and the shortcomings of dealumination as described above cannot be solved, with the low catalytic activities remaining as they are. This means that the binder works merely as a dispersant of the zeolite, and the catalytic activities depend on the dealuminated zeolite whose active points are decreased by the dealumination.